1. Field of the Invention
The present invention relates to a control and monitoring system installed in a plant and the like having a monitoring target such as a substation.
2. Description of the Related Art
Typically, a control and monitoring system is arranged to constantly monitor the operating state of key equipments, which are determined to be monitoring targets, inside, e.g., a substation that is necessary in maintaining a stable power supply. The monitoring result of the control and monitoring system provides information such as occurrence of a malfunction state or recovery from a malfunction state to a system operator and record. The history of such monitoring results can be used for maintenance and repair of the monitoring targets or for statistical analysis. Moreover, the significance of performing constant monitoring is to enable the system operator to immediately take necessary actions in case a monitoring target falls in a malfunction state. That helps in minimizing the possible adverse effect on other equipments. Thus, it is important that the control and monitoring system promptly notifies the system operator of any malfunctioning monitoring target and provide correct details of the malfunction state.
In response to the detection of a malfunction state of a monitoring target, a conventional control and monitoring system obtains malfunction state contact information from the monitoring target, compares the amount of current or the amount of voltage output by the monitoring target with internal predetermined values, and, if the values do not match, issues a warning to the system operator. Moreover, the control and monitoring system includes a human-machine interface (HMI) unit on which changes in the operating state of the monitoring target are displayed in the form of changes in particular symbols and the details of those changes are listed as textual messages. That enables the system operator to learn about the malfunction state of the monitoring target.
The control and monitoring system records information about changes in the operating state of the monitoring targets (e.g., falling in a malfunction state or recovering from a malfunction state). The recorded information includes textual messages providing the date and time at which the changes occurred and the identification information of the monitoring targets in which the changes occurred along with the changed operating states (malfunction state or recovered state) of the identified monitoring targets. The control and monitoring system stores the recorded information or displays the recorded information on the HMI unit.
For example, Japanese Patent Application Laid-open No. S58-29012 discloses a malfunction displaying technique for displaying a malfunction state of a plant. Similarly, Japanese Patent Application Laid-open No. 2002-373021 discloses a warning displaying technique for displaying the results of monitoring the operating state of a plant.
As described above, in a conventional control and monitoring system, information about changes in the operating state of the monitoring targets is recorded as textual messages that provide the date and time at which the changes occurred and the identification information of the monitoring targets in which the changes occurred along with the changed operating states (malfunction state or recovered state) of the identified monitoring targets. The recorded information is stored or displayed as a message list on the HMI unit. In case a monitoring target accidentally falls in a malfunction state, the recorded information is used to analyze the cause of the accident. For that, the system operator has to search the message list for the message that indicates malfunctioning of the particular monitoring target, the time at which the message was generated, and any other messages that provide details of previous changes in the operating state of the same monitoring target. However, usually, an accident causes changes in the operating state of more than one monitoring targets. Moreover, the list includes messages corresponding to a plurality of monitoring targets, some of which may not get affected by the accident. Thus, the task of searching messages that provide details of the monitoring targets affected by the accident is not easy.
Moreover, the information provided by the messages is textual information and the messages are displayed as a list on the HMI unit to provide as much information to the system operator as possible. Thus, recognizing the messages by the corresponding character string (textual information) and searching for desired messages from the list consumes a lot of time. Furthermore, in a stressful emergency situation at the time of an accident, there is a risk that relevant messages are overlooked during the search or a character string is falsely recognized as a similar but different character string.
Meanwhile, a waveform recording device is also used for monitoring an electric power equipment. The waveform recording device performs rapid recording of current waveforms or voltage waveforms at periodic sampling timings. However, due to the limitations in physical storage capacity, it is necessary to specify in advance the signals to be recorded and the triggers to be used for storing the recorded signals. Moreover, it is also necessary to record various combinations of signals in response to the possibility of a plurality of malfunctions. Furthermore, because a waveform recording device displays all specified signals, the displayed signals include signals that are not necessary for analysis at that particular point of time thereby making the analysis job complicated.
In Japanese Patent Application Laid-open No. S58-29012, a method to perform trend display within a predetermined time period or starting from an arbitrary time instant is described by operating a display switching unit (see FIG. 5 in Japanese Patent Application Laid-open No. S58-29012). However, because the display switching unit and an HMI unit used to display warning messages are arranged in a mutually isolated manner, the displayed information lacks in coherency. Moreover, because the system operator is required to perform operations while comparing apparently similar textual information displayed in the list of warnings, there is a risk of errors occurring during normal operations. Furthermore, the trend display within a predetermined time period cannot be considered as the suitable display format because the displayed information may include information that the system operator does not require at that particular point of time.
In Japanese Patent Application Laid-open No. 2002-373021, description is given regarding a warning displaying device that displays a warning history page including the history of warnings (see FIG. 24 in Japanese Patent Application Laid-open No. 2002-373021). However, there is no description about displaying only those warning messages that are required by the system operator. That is, because the warning messages are displayed by obtaining information from a history table (see paragraph no. 119 in Japanese Patent Application Laid-open No. 2002-373021), the displayed warning messages includes information not required by the system operator at that point of time. Meanwhile, a warning storage unit includes a target warning specifying unit that is used to arbitrarily specify and store current warnings and a displaying unit is used to display the stored information (see paragraph no. 39 in Japanese Patent Application Laid-open No. 2002-373021). However, that process involves two steps, namely, a step of storing warnings and a step of selecting warnings for display. Moreover, the operations for carrying out those steps are not described in detail.
In this way, in a conventional monitoring system, the detailed information about changes in the operating state of monitoring targets is displayed in the form of a list of textual messages. The display of a list of textual messages is suitable for efficiently providing as much information as possible at once to the system operator. However, because the necessary details are displayed only in the form of textual messages, it is difficult to get an idea about the temporal sequence of changes in the operating state of a particular monitoring target. Moreover, although it is possible to display the textual messages in chronological order, it still does not serve the purpose of displaying only the required information in an easy and correct manner and in a short amount of time.